With a diameter of about 950 km, Ceres is by far the largest and most massive object in the asteroid belt, and has about a third of the belt's total mass. It was once thought to be smaller than Vesta, which is brighter. The asteroid is spherical, unlike the irregular shapes of smaller bodies with lower gravity. At its brightest it is still too dim to be seen with the naked eye.[11]

On September 27, 2007, NASA launched the Dawn space probe to explore Ceres and Vesta. In 2015, Dawn became the first spacecraft to visit a dwarf planet, arriving at Ceres a few months before NASA's New Horizons spacecraft visited Pluto, another dwarf planet.